| 1. |
- Forsberg, Jens, et al.
(author)
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Redox signalling in chloroplasts and mitochondria: genomic and biochemical evidence for two-component regulatory systems in bioenergetic organelles
- 2001
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In: Biochemical Society Transactions. - 0300-5127. ; 29:4, s. 403-407
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Journal article (peer-reviewed)abstract
- Redox chemistry is central to the primary functions of chloroplasts and mitochondria, that is, to energy conversion in photosynthesis and respiration. However, these bioenergetic organelles always contain very small, specialized genetic systems, relics of their bacterial origin. At huge cost, organellar genomes contain, typically, a mere 0.1% of the genetic information in a eukaryotic cell. There is evidence that chloroplast and mitochondrial genomes encode proteins whose function and biogenesis are particularly tightly governed by electron transfer. We have identified nuclear genes for 'bacterial' histidine sensor kinases and aspartate response regulators that seem to be targeted to chloroplast and mitochondrial membranes. Sequence similarities to cyanobacterial redox signalling components indicate homology and suggest conserved sensory and signalling functions. Two-component redox signalling pathways might be ancient, conserved mechanisms that permit endogenous control over the biogenesis, in situ, of bioenergetic complexes of chloroplasts and mitochondria.
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| 3. |
- Johanson, Urban, et al.
(author)
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The complete set of genes encoding major intrinsic proteins in Arabidopsis provides a framework for a new nomenclature for major intrinsic proteins in plants
- 2001
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In: Plant Physiology. - : Oxford University Press (OUP). - 1532-2548 .- 0032-0889. ; 126:4, s. 1358-1369
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Journal article (peer-reviewed)abstract
- Major intrinsic proteins (MIPs) facilitate the passive transport of small polar molecules across membranes. MIPs constitute a very old family of proteins and different forms have been found in all kinds of living organisms, including bacteria, fungi, animals, and plants. In the genomic sequence of Arabidopsis, we have identified 35 different MIP-encoding genes. Based on sequence similarity, these 35 proteins are divided into four different subfamilies: plasma membrane intrinsic proteins, tonoplast intrinsic proteins, NOD26-like intrinsic proteins also called NOD26-like MIPs, and the recently discovered small basic intrinsic proteins. In Arabidopsis, there are 13 plasma membrane intrinsic proteins, 10 tonoplast intrinsic proteins, nine NOD26-like intrinsic proteins, and three small basic intrinsic proteins. The gene structure in general is conserved within each subfamily, although there is a tendency to lose introns. Based on phylogenetic comparisons of maize (Zea mays) and Arabidopsis MIPs (AtMIPs), it is argued that the general intron patterns in the subfamilies were formed before the split of monocotyledons and dicotyledons. Although the gene structure is unique for each subfamily, there is a common pattern in how transmembrane helices are encoded on the exons in three of the subfamilies. The nomenclature for plant MIPs varies widely between different species but also between subfamilies in the same species. Based on the phylogeny of all AtMIPs, a new and more consistent nomenclature is proposed. The complete set of AtMIPs, together with the new nomenclature, will facilitate the isolation, classification, and labeling of plant MIPs from other species.
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